WASHINGTON (AP) -- Pivotal Supreme Court Justice Anthony Kennedy did not tip his hand Tuesday as the high court heard historic arguments over the right of gay and lesbian couples to marry.
Kennedy, whose vote could decide the issue, offered reasons for hope to both sides in the courtroom. Same-sex couples now can marry in 36 states and the District of Columbia, and the court is weighing whether gay and lesbian unions should be allowed in all 50 states.
Kennedy seemed to share the concern of the court's conservative justices when he said marriage has been understood as one man and one woman for "millennia-plus time." Same-sex marriage has been around in the United States for just over 10 years, and he wondered aloud whether scholars and the public need more time.
"This definition has been with us for millennia. It's very difficult for the court to say, well, we know better," Kennedy told Mary Bonauto, a lawyer arguing on behalf of same-sex couples.
Yet Kennedy also pressed attorney John Bursch, representing the states that ban same-sex marriage, to explain how granting gay couples a right to marry would harm traditional marriages. Bursch argued that removing child-rearing as the central rationale for marriage would weaken parents' commitment to staying married for their children's sake if their own ties were frayed.
Kennedy seemed concerned about adopted children in same-sex households in which only one partner is considered a parent by Michigan. "Under your view, it would be very difficult for same-sex couples to adopt those children," Kennedy said.
Chief Justice John Roberts also directed questions to both sides that made it hard to predict where he will come down.
Roberts said gay couples seeking to marry are not seeking to join the institution of marriage. ""You're not seeking to join the institution - you're seeking to change what the institution is. The fundamental core of the institution is the opposite sex relationship and you want to introduce into it a same sex relationship." he said to Bonauto.
But Roberts also questioned the states' argument, asking, "If Sue loves Joe and Tom loves Joe, Sue can marry him and Tom can't. Why isn't that a case of sexual discrimination?"
The arguments offered the first public indication of where the justices stand in the dispute over whether states can continue defining marriage as the union of a man and a woman, or whether the Constitution gives gay and lesbian couples the right to marry.
In general, the conservative justices indicated their support for the states, while the court's liberals signaled they would find that same-sex couples should be allowed to marry in all 50 states.
Justice Samuel Alito suggested that basing marriage on lasting bonds and emotional commitment - instead of providing stable homes for children - might open the right to marry to siblings who live together, close friends who are not romantically or sexually involved and groups of more than two people.
Justice Antonin Scalia said he worried that a court decision in favor of same-sex marriage would force ministers to stop officiating at weddings altogether if they refused to perform same-sex weddings. Bonauto and some of Scalia's colleagues tried to persuade him that ministers have a right to refuse any couple for religious reasons.
Scalia also said the issue is not whether there should be same-sex marriage "but who should decide the point," embracing the states' argument.
Among the liberals, Justices Stephen Breyer and Sonia Sotomayor both said marriage was a fundamental right and a state would need a truly compelling reason to deny it to a class of people.
The session was interrupted after about 30 minutes by an anti-gay marriage protester who yelled that supporters of gay marriage "will burn in hell." He was removed by security.
The last part of Tuesday's session was to focus on whether states that do not permit same-sex marriage must nonetheless recognize such unions from elsewhere.
People on both sides of the issue gathered outside the marble courthouse.
"Homo sex is a sin," read one demonstrator's sign. A man shouted into a microphone that gays violate the laws of God. A group of same-sex advocates tried to drown him out by singing "The Star-Spangled Banner."
Cheers went up in the crowd when the court's doors opened, allowing a lucky few who lined up days ago to get inside.
The cases before the court come from Kentucky, Michigan, Ohio and Tennessee, four of the 14 remaining states that allow only heterosexual marriage. Those four states had marriage bans upheld by the federal appeals court in Cincinnati in November. That is the only federal appeals court that has ruled in favor of the states since the Supreme Court in 2013 struck down part of the federal anti-gay marriage law.
Kennedy has written the court's three prior gay rights decisions, including the case from two years ago. All eyes are on him for any signals of his intention this time.
It was barely a decade ago that the first state allowed gay and lesbian couples to marry. That was Massachusetts, in 2004. As recently as last October, barely a third of the states permitted it. Now, same-sex couples can marry in 36 states and Washington, D.C., a sign of the dramatic change in public opinion.
At the Supreme Court, the opposing states hoped to reframe the debate.
"This case is not about the best marriage definition. It is about the fundamental question regarding how our democracy resolves such debates about social policy: Who decides, the people of each state or the federal judiciary?" John Bursch, representing Michigan, wrote in his main brief to the court.
The push for same-sex marriage comes down to fairness, said Bonauto, who argued on behalf of the plaintiffs. The people who have brought their cases to the Supreme Court are "real people who are deeply committed to each other. Yet they are foreclosed from making that commitment simply because of who they are," she told reporters last week.
Arguments made by Bonauto, other lawyers for same-sex couples and more than six-dozen supporting briefs have strong echoes of the 1967 Loving v. Virginia case, in which the Supreme Court struck down state bans on interracial marriage. In that case, the justices were unanimous that those bans violated the constitutional rights of interracial couples.
No one expects unanimity this time. The justices have allowed orders in favor of same-sex couples to take effect even as the issue has made its way through the federal court system, but that was action through inaction.
Only 11 states have granted marriage rights to same-sex couples through the ballot or the legislature. Court rulings are responsible for all the others.
A decision is expected in late June.